Electrical conductors at high voltage are surrounded by electric fields that are more concentrated, i.e., have higher voltage gradients, in the vicinity of sharp points or small radii of curvature of electrodes, terminals, or conductive components of the circuit. If the voltage gradient is high enough, the air surrounding these points will be ionized, and a corona discharge will develop which may lead to a flashing spark or arc discharge to another conductor at a different potential. The use of toroidal metallic corona rings around these vulnerable points in order to minimize electrical discharging is common practice. However, the metal corona rings frequently are insufficient to prevent flash discharging. This invention uses dielectric corona rings to provide a significant improvement over the prior metal type corona rings, and thus increase the insulating capability of high voltage insulators.